Multiple-Input Multiple-Output (MIMO) transmissions have been proposed for fourth generation (4G) wireless communication systems. Unlike third generation (3G) wireless communication systems, where a single amplifier may amplify a signal that then is distributed to multiple elements of an antenna array, a MIMO transmitter conveys a different signal via each antenna of multiple antennas of an antenna array and correspondingly requires multiple amplifiers, that is, an amplifier for each antenna. However, as 4G wireless communication systems get rolled out, the 4G base station transmitters will have to service legacy communication technologies as well as a fourth generation communication technology. As a result, operation of a 4G base station will involve single antenna transmissions as well as multiple antenna transmissions. Single antenna transmissions merely require use of a single amplifier, with the result that the additional amplifiers included in the base station that supports MIMO transmissions will go unused in non-MIMO transmissions.
As MIMO wireless communication systems are rolled out, most transmissions will be legacy transmissions. Amplifiers are costly components of a base station and a failure to use, in a non-MIMO transmission, the multiple amplifiers that are available for MIMO transmissions is a waste of expense and hardware. Also, by amplifying a non-MIMO signal using a single amplifier, larger and more costly amplifiers are required than would be required if such a single was amplified using multiple amplifiers.
Therefore a need exists for a method and apparatus that utilizes all amplifiers of a MIMO transmitter regardless of whether or not a transmission is a MIMO transmission and that further allocates power gains among the multiple antennas of the MIMO transmitter.
One of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.